Otitis media, sinusitis, bronchitis, pharyngitis, and nonspecific upper respiratory tract infections (URTI) account for approximately 75% of outpatient antibiotic prescriptions in the United States. Antibiotic use remains high despite the fact that greater than 85% of these infections are due to viruses and resolve without complication. Nonetheless, those remaining infections that are indeed due to bacterial pathogens require more effective management than is currently available. Bacterial cultures provide limited diagnostic value because the most common bacteria responsible for URTI are also often commensal organisms in the nasopharynx.
Infections of the upper airway are the number one reason for office visits in the US (American Academy of Pediatrics. Pediatrics, 2004. 113:1451-1456, Center for Disease Control and Prevention web site, Gonzales R, et al. JAMA, 1997. 278(11):901-904, Nyquist A-C. JAMA, 1998. 279(11): 875-877). About 52% of adults patients and 45% of pediatric patients are prescribed antibiotics when diagnosed with an upper airway infection (Gonzales R, et al. JAMA, 1997. 278(11):901-904, Nyquist A-C. JAMA, 1998. 279(11): 875-877). Upper airway infections are multifactorial and polymicrobial diseases. Infection by respiratory viruses (e.g. RSV, adenovirus, rhinovirus, parainfluenza virus) predisposes to bacterial superinfection by members of the nasopharynx normal flora: nontypeable Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis. While viral infections are often self-limiting, therapeutic delay of bacterial disease can lead to complications, permanent sequalae and severe morbidity and mortality.
Diagnosis is mainly based on clinical manifestations. Signs and symptoms of disease of bacterial and nonbacterial etiologies are often indistinguishable. Specific bacterial identification by traditional microbiological culture techniques often fail to detect microorganisms growing within biofilms. Contamination of specimens by resident colonizing flora often results in laboratory culture reports of uncertain clinical value. Indiscriminate antibiotic use modifies the commensal flora in the nasopharynx and induces the selection and emergence of microorganisms resistant to common antibiotics. Despite a decreasing trend in antibiotic prescription in recent years, unnecessary and inappropriate antibiotic therapies are common, particularly in the treatment of otitis media and sinusitis.
Upper respiratory tract infection remains as a major cause of overuse of antibiotics and, therefore, a major contributor to the widespread emergence of antibiotic resistance. Therefore, there is a need for early and rapid diagnostic tests that could discriminate between commensal and pathogenic bacteria. These tests would promote judicious use of antibiotic therapy, promote more effective choice of treatment and improve outcomes.